Quantitative Aptitude: Boats and Streams Questions Set 6

  1. A boat takes half time in moving a certain distance downstream than upstream. What is the ratio between rate of boat in still water and rate of current?
    2:3
    3:1
    2:1
    3:5
    None
    Option B
    Solution:
    Let the distance be xkm.
    Then
    2x/(u+v) = x/ (u-v)
    2u – 2v = u+v
    u:v=3:1.
  2. A boat covers a certain distance downstream in 2 hour, while it comes back in 2 1/2 hours. If the speed of the stream be 3 km/hr, what is the speed of the boat in still water?
    20km/hr
    23km/hr
    27km/hr
    30km/hr
    None
    Option C
    Solution:
    Speed downstream = (u + 3) km/hr
    Speed upstream = (u- 3) km/hr
    (u+ 3) *2 = (u- 3) *5/2
    4u+12=5u-15
    u=27km/hr.
  3. If sum of upstream and downstream speed of a boat is 82 kmph, and the boat travels 105 km. upstream in 3 hr, Find the time taken by boat to cover 141 km downstream.
    5hrs
    4hrs
    3hrs
    2hrs
    None
    Option C
    Solution:
    Speed of Upstream =u-v
    Speed of Downstream = u+v
    u-v+u+v=82
    2u=82
    u=41km/hr.
    41 – v = 105/3 = 35
    v = 6 km/hr
    then,
    u + v= 141/t
    41 + 6 = 141/t
    t = 141/47 = 3 hrs.
  4. A boatman goes 4 km against the current of the stream in 1 hour and goes 2 km along the current in 10 minutes. How long will it take to go 24 km in stationary water?
    5hrs
    3hrs
    2hrs
    6hrs
    None
    Option B
    Solution:
    Upstream=4/1=4km/hr
    Downstream=2*60/10=12km/hr
    Speed in still water=(12+4)/2
    =16/2=8km/hr.
    For 24 km time=24/8
    =3hrs.
  5. The speed of a boat in still water is 15 km/hr. It can go 30 km upstream and return downstream to the original point in 4 hrs 30 min. The speed of the stream is:
    12km/hr
    8km/hr
    5km/hr
    10km/hr
    None
    Option C
    Solution:
    D=t [(u2 – v2) /2u] 30 = 4 ½ *[(152 – v2) /2*15] 30=9/2 (225- v2)/30
    200=225- v2
    v2=25
    v=5km/hr.
  6. A boat takes 12 hr to travel a distance upstream and takes 6 hr to travel the same distance downstream. If the speed of the boat in still water is 4 kmph, then what is the speed of the stream?
    5km/hr
    1km/hr
    3km/hr
    2km/hr
    None
    Option B
    Solution:
    6(3+v) = 12(3-v)
    18 +6v=36-12v
    18v=18
    v=1km/hr.
  7. A man can row 8 km/hr in still water. If it takes him thrice as long to row up, as to row down the river, then the rate of current in the stream would be
    6.5km/hr
    4.5km/hr
    4km/hr
    5.5km/hr
    None
    Option C
    Solution:
    Ratio 3:1
    u=8km/hr
    (8-v)*3t = (8+v)*t
    24-3v=8+v
    4v=16
    v=4km/hr.
  8. A man can row three-quarters of a kilometer against the stream in 45/4 minutes and return in 15/2 minutes. The speed of the stream
    1km/hr
    3km/hr
    5km/hr
    4km/hr
    None
    Option A
    Solution:
    Upstream in 45/4min=3/4km
    In 1 hr =3/4*4/45*60
    =4km/hr.
    Downstream in 15/2min=3/4km
    In 1 hr=3/4*2/15*60
    =6km/hr.
    V=(6-4)/2
    =2/2
    =1km/hr.
  9. A boat running downstream covers 28 kms in 7 hours, while for covering the same distance upstream it takes 4 hours. What is the speed of the boat in still water and ?
    4km/hr
    4.5km/hr
    5km/hr
    5.5km/hr
    None
    Option D
    Solution:
    Downstream=28/7=4km/hr
    Upstream=28/4=7km/hr
    Speed of the boat u=(4+7) /2
    =11/2=5.5km/hr.
  10. A man can row 8 km/hr in still water. If the river is running at 3 km/hr, it takes 3 hours more in upstream than to go downstream for the same distance. How far is the place?
    27.5km
    29km
    31.5km
    33km
    None
    Option A
    Solution:
    D=3 (82 -32)/(2*3)
    =(55*3)/6
    =27.5km.



 

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